1. Field of the Invention
The present invention relates to the suppression of an audio induced interference for video display appliances. In particular, the present invention relates to an apparatus for suppressing the audio induced interference which may be produced in a color picture tube due to the transfer of vibrations arising from the output of a loudspeaker provided in a loudspeaker case directly adjacent to the color picture tube by absorbing and dampening the vibrations generated from the loudspeaker.
2. Description of the Prior Art
Video display appliances such as monitors, television receivers, etc., are typically provided with a color picture tube (CPT). Such video display appliances may be also provided with at least one loudspeaker for the output of sound.
FIGS. 1 to 3 are views illustrating a conventional video display appliance in an assembled state.
Referring to FIGS. 1 to 3, the conventional video display appliance comprises a main body 60 provided with a color picture tube (CPT) 1, a cabinet 10 assembled with the CPT 1, and a back cover 20 assembled with the cabinet 10 by being secured to the rear of the CPT 1; a tilting swivel 30 mounted on the bottom portion of the main body 60, for adjusting the right and left rotation and the upward and downward tilting of the main body 60; and loudspeaker cases 50, provided on both sides of the main body 60, for protectively supporting loudspeakers 40 respectively installed therein.
Referring again to FIG. 3, the cabinet 10 is provided with CPT-fastening bosses 11, formed inside the cabinet 10, for fastening to CPT lugs 2 formed on a CPT 1 by fastening screws 3A, and back cover fastening bosses 12 projected from inner sides of the cabinet 10 so as to be fastened to a back cover 20.
The back cover 20 is provided with fastening holes 21 formed on both sides of the back cover 20 to fix the loudspeaker cases 50 to the back cover 20 by fastening screws 3B passing therethrough, and cabinet-fastening bosses 22 projected from inner sides of the back cover 20 so as to be fastened to the back cover fastening bosses 12 by fastening screws 3C.
The loudspeaker case 50 is provided with inner and outer walls 51 and 52 for surrounding the loudspeaker 40, through holes 53, formed on the loudspeaker case 50, for fitting with the fastening holes 21 to fix the loudspeaker case 50 to the back cover 20 by fastening screws 3B, loudspeaker fastening bosses 54 projected from the inner side of the loudspeaker case 50 to fix the loudspeaker 40 thereto by fastening screws 3D, and loudspeaker grilles 55 provided on the front of the loudspeaker case 50 to pass therethrough the sound outputted from the loudspeaker 40.
In the drawing, the numeral 56 denotes an inner cover fastening hole.
According to the conventional video display appliance as constructed above, the CPT lugs 2 projected from both sides of the CPT 1 mate with and are fastened to the CPT fastening bosses 11 projected from the inside of the cabinet 10 by the fastening screws 3A, resulting in that the cabinet 10 is assembled on the front of the CPT 1.
Thereafter, the cabinet fastening bosses 22 projected from both inner sides of the back cover 20 mate with and are fastened to the back cover fastening bosses 12 projected from both inner sides of the cabinet 10 by the fastening screws 3C, so that the back cover 20 on whose lower part the tilting swivel 30 is assembled is fastened to the cabinet, covering the rear portion of the CPT 1.
Meanwhile, the loudspeaker 40 mates with and is fastened to the loudspeaker fastening bosses 54 projected from the inner side 51 of the loudspeaker case 50 by the fastening screws 3D, so that the loudspeaker 40 is fixed inside the loudspeaker case 50.
At this time, after the loudspeaker cases 50 in which the loudspeakers 40 are respectively fixed are brought into contact with both sides of the back cover 20 and the cabinet 10 assembled on the CPT 1, the fastening holes formed on both sides of the back cover 20 mate with the through holes 53 formed through the inside and outside surfaces 51 and 52 of the loudspeaker case 50, a fastening screw 3B is inserted into and secured to the fastening hole 21 and the through hole 53, so that the cabinet 10, the back cover 20, and the loudspeaker case 50 are completely assembled together as shown in FIG. 2.
When the conventional video display appliance as constructed above operates, video information is displayed on the CPT 1 and an audio signal from the loudspeaker 40 is outputted through the loudspeaker grille 55 provided on the front of the loudspeaker case 50. At this time, vibrations which correspond to the level of the outputted audio signal are produced from the loudspeaker 40 and directly transferred to the CPT 1.
The tilting swivel 30 adjusts the right and left rotation and the upward and downward tilting of the main body 60 of the video display appliance. However, the tilting swivel 30 cannot serve as a vibration absorbing or reducing device.
The vibrations produced from the loudspeaker 40, as shown in FIG. 3, are transferred to the loudspeaker fastening boss 54 through the screw 30 which is fastened to the loudspeaker fastening boss 54 projected from the loudspeaker case 50 to fix the loudspeaker 40 thereto, and then are transferred to the screw 3E fastened through the through hole 53 via the outer surface 52 of the loudspeaker case 50.
Thereafter, the vibrations having reached the screw 3E secured through the through hole 56 of the loudspeaker case 50 pass through the inner side surface 51 and then are transferred to the screw 3B through the contacted surface ("C" portion of FIG. 3) of the back cover 20 and the loudspeaker case 50 and/or through the screw 3B fastened through the fastening hole 21 of the back cover 20 and the through hole 53 of the loudspeaker case 50.
The vibrations having reached the back cover 20 are transferred to the cabinet 10 through the screw 3C fixed to the back cover fastening boss 12 projected from both sides of the cabinet 10 and the cabinet fastening boss 22 on both sides of the back cover 20, and then along the contacted surface ("B" portion of FIG. 3) of the cabinet 10 and the back cover 20 assembled together. The vibrations transferred to the cabinet 10 are then transferred to the CPT lug 2 through the screw 3A fastened to the CPT fastening boss 11 and reach a shadow mask provided on the CPT, passing through the contacted surface ("A" portion of FIG. 3) of the CPT 1 and the cabinet 10.
At this time, three electron beams for red, green, and blue colors, which are emitted from electron guns of the CPT 1, are directed to the fluorescent screen of the CPT 1 through beam-passing apertures provided on the shadow mask. The electron beams are affected by the vibrations transferred to the shadow mask, and thereby the interference, i.e., the howling phenomenon is produced on the screen of the CPT 1.
The interference deteriorates the picture quality and fatigues a user's eyes easily. Further, it limits the scale of the CPT screen and the output level of the loudspeaker.